During recent years chlorine dioxide has been proposed for use as an oxidant in a variety of well treating operations. These treatments, however, have generally involved the removal of formation damage caused by polymer deposits. For example, U.S. Pat. No. 4,871,022 discloses the use of chlorine dioxide to degrade polymer deposits encountered in secondary and tertiary recovery operations. U.S. Pat. No. 4,846,981 discloses a similar use of chlorine dioxide in well acidizing operations. Canadian Patent No. 1,207,269 discloses the use of chlorine dioxide in the separation of oil and water in oil producing operations. Chlorine dioxide has also been used as a scavenger for hydrogen sulfide as described in U.K. Patent Application No. 2170220A.
Other oxidants used in well treating processes include sodium hypochlorite, (U.S. Pat. Nos. 3,486,636; 3,29,669; 3,556,221), hydrogen peroxide, (U.S. Pat. No. 4,464,268).
As described in detail below, the use of chlorine dioxide in accordance with the present invention results in formation stimulation by reacting with clays, silicaeous materials, sand, drilling mud, or cement filtrate. The treatment has the same objective as treatments using mud acid (mixture of HF and HCl), but accomplishes the improvement by entirely different chemistry. The chlorine dioxide treatment according to the present invention, moreover, offers several advantages over mud acid treatments: (a) it is much less expensive, (b) it avoids the hazards and toxicity of HF, and (c) it avoids the deposits such as sodium or potassium fluorosilicates and CaF.sub.2.